It is known practice to dye keratin fibers, such as human hair, with dye compositions containing oxidation dye precursors, generally known as “oxidation bases.” Representative “oxidation bases” are ortho- or para-phenylenediamines, ortho- or para-aminophenols and heterocyclic bases.
Oxidation dye precursors are compounds which are initially uncoloured or only weakly coloured and which develop their dyeing power on the hair in the presence of oxidizing agents leading to the formation of coloured compounds. The formation of these coloured compounds results either from an oxidative condensation of the “oxidation bases” with themselves or from an oxidative condensation of the “oxidation bases” with coloration modifiers, or “couplers”, which are generally present in the dye compositions used in oxidation dyeing and are represented by meta-phenylenediamines, meta-aminophenols and meta-diphenols, and certain heterocyclic compounds.
The variety of molecules used, which comprise on the one hand the “oxidation bases” and on the other hand, the “couplers”, allows a very wide range of colours to be obtained.
These oxidation bases and these couplers are formulated in vehicles that allow them to be applied to keratin fibers after mixing with an oxidizing agent.
These vehicles are generally aqueous and can comprise one or more surfactants, such as nonionic surfactants, that may be optionally combined with one or more solvents.